1. Field of Invention
This invention relates to a movable crane. More specifically, it is directed to a pedestal or kingpost type luffing crane having a support that removably mates with a stationary receiving socket and, thereby, permits the movement of the crane from one receiving socket to another.
Presently, a number of applications need a high capacity crane that may be moved from location to location. For example, in construction that requires the use of very large capacity cranes, the cranes are transported to and temporarily mounted at the worksite. Typical of such cranes are platform ringer cranes. The platform ringer cranes include a platform rotatably mounted on a large diameter ring that has a bearing therein. The platform supports the upperworks of the crane that consists of a crane boom, the power and control devices, and the counterweights. The large diameter ring typically mounts on an above ground foundation and, thus, is gravity supported. Therefore, the platform ringer crane must include sufficient counterweight to counterbalance any weight supported at the end of the boom such that the center of gravity remains within the ring. As a result, the platform ringer cranes are extremely large and require dozens of trucks to transport.
Often, after the platform ringer crane has performed its function, the foundation remains in place for future work requiring the crane. As mentioned, the cranes, as well as the associated foundations, are extremely large. Thus, the foundation occupies substantial space making that space unusable. Therefore, providing a high capacity crane that is easier to move and permits the use of the space previously occupied by the crane eliminates these problems.
A second example of an application that needs a removable crane is in Naval transport ships. To increase its preparedness, the Navy instituted a program of fitting civilian ships with cranes. In times of war, the ships could transport goods for the war effort and load and unload the goods at any place designated by the Navy. Fitting the substantial number of ships required to supply a war effort is extremely costly due to the cost of the cranes as well as the amount of supplies required for an effective campaign. In addition, the ships, with the cranes affixed thereto, travel the world in times of peace subjecting the cranes to the harsh open sea environment. Consequently, the crane supplies of the Navy become worn and fall into disrepair because they are stored in this harsh environment.
However, the expense of providing and maintaining the cranes could be reduced by providing movable cranes. The pertinent ships could be fitted to receive the movable cranes; and the cranes could be stored in warehouses until needed. Then in times of need, the cranes could be quickly affixed to the ships for use.
A third example of an application needing a movable crane is in a merchant ship application. Many merchant ships include large capacity cranes thereon to provide for loading and unloading in ports that are not equipped with cranes. However, like in the Navy ships described above, these cranes are not needed at all times and are subjected to harsh environments. Thus, a fleet of merchant ships could share a supply of movable cranes. Additionally, the movable cranes could be stored protecting them from the elements when not needed.
U.S. Pat. No. 5,310,067 that issued to applicant herein, describes the development of kingpost cranes. As described, cranes with vertically separated bearing assemblies, such as kingpost cranes, are considered an alternative to mobile cranes. The advantages and need for the higher load capacity, safety, and stability of kingpost cranes is also described in the '067 patent. Likewise, U.S. Pat. No. 4,354,606 shows a pedestal crane. Like the kingpost in a kingpost crane, the pedestal of a pedestal crane mounts in a large fixed foundation and support such as the ground, the deck of a ship, or the deck of a loading dock. Thus, the kingpost and pedestal cranes are embedded in the foundation and not transportable.
Frequently, kingpost and pedestal cranes operate in maritime shipping, offshore, and other environments where space utilization efficiency is often crucial. The cranes require substantial space and are limited in both maximum and minimum operating distance from the kingpost or pedestal. A mobile kingpost or pedestal crane would not only provide the advantages of an embedded crane; but the kingpost or pedestal crane's mobility would additionally provide the advantage of increasing the operating distance of the embedded crane and would make available the space generally occupied by the embedded crane. Thereby, a mobile embedded crane would increase the space utilization efficiency.
Typically, due to the limited operating distance of an embedded crane, a number of cranes are often required to operatively service a given area. However, because the embedded cranes are relatively expensive, providing sufficient crane service area is often costly. Thus, a mobile embedded crane would reduce the number of embedded cranes required for a given area and, thereby, reduce the cost of providing cranes for a specified area.
2. Related Art
Although mobile cranes are commonly known to the prior art, the prior art does not disclose a luffing crane, of the kingpost or pedestal type, which is attachable to a socket in the ground, may be readily moved from one socket location to other socket locations without the need to disassemble the crane or its components, and retains the capacity and stability to support a relatively large load. Illustrative of prior art cranes are U.K. Patent Number 10,730 that issued to Purdy in May, 1894, U.K. Patent Number 2,177,374A that issued to Fluemer in January, 1987, U.S. Pat. No. 2,699,875 that issued to Stratton in January, 1955, U.S. Pat. No. 3,160,284 that issued to Moore in December, 1964, U.S. Pat. No. 4,354,606 that issued to Morrow et al. in December, 1977, U.S. Pat. No. 4,061,230 that issued to Goss et al. in December, 1977, and U.S. Pat. No. 5,310,067 that issued to Morrow in May, 1994.
Though the above mentioned cranes may be helpful for their intended purpose, they can be improved to provide mobility while maintaining the advantages of an embedded crane and, thereby, provide greater space utilization and lower cost.